@mcgraffy got me thinking about whale watching gone wrong experiences; you'll be happy to know that I couldn't find any info about whales flipping boats, but I did find this video.
In the video, a whale is very close to a small boat, just swimming around, and when it finally dives back into the water, its tail fin flips up and hits a girl in the head. Seriously!
I couldn't help but laugh--it seems like she was fine, and the slow motion just....well its so funny!
Hope you enjoy :)